I think these cases have a higher copper composition than usual. Not sure if that has anything to do with the neck splits or if they split because they originally had a higher neck tension than normal because the bullets have no cannelure thus no crimp.
I can tell you that I sold my Halger for $4600 which looking back I feel was too low. I should have kept it really although it was quite heavy and impossibly long by today's standards. Long barrel, long action, long forend, and a long length of pull. Often wondered just who ordered it that way. Guy must have been 6'5"...